Blender game engine, shape key driver
It's not done with drivers. In the script I see:


  own.channels["eye"].location = 0.0, own["eye"], 0.0
  own.channels["smile"].location = 0.0, own["smile"], 0.0


channels is a list of the bones in the armature.
I think he has parented the vertices to the bones and moved the bone channels.
Or maybe he has bound the bones to the drivers.